The first three missions of NASA’s next big rocket will have to settle for a less-powerful ride

The first three missions of NASA’s next-generation rocket, the Space Launch System, will all fly on the least powerful version of the vehicle that the space agency plans to build. NASA is moving forward with its plan to use a downgraded version of the SLS for its second and third flights, according to a memo from NASA headquarters obtained by The Verge. The original plan was to fly those two flights on a much more powerful upgrade of the rocket, but now, it seems that version won’t debut until 2024 at the earliest.

The SLS, meant to take humans into deep space, has been under development for the last decade, with its first three missions mostly set in stone. For its debut flight, called EM-1 and scheduled for 2020, the rocket will send…